Rather disappointed that nobody has yet taken the moral approach to this. Obviously before taking any physical action you should provide them with notice to evict and allow them a timely manner in which to vacate.
If they refuse to do so, send in the bailiffs.
Poo through your air brick and own letterbox. Rub mustard on your own poo and show it to the neighbors, tell them the voices told you to .
Déjà pu.
Smear a bit of mustard around the brickwork as this will put them off. It has to be English Mustard as these may be french wasps.